Winding configuration electric motor

ABSTRACT

A stator assembly for a permanent magnet motor is disclosed. The assembly comprises a yoke comprising a plurality of teeth in connection therewith and extending into an opening formed by the yoke. The plurality of teeth comprises a first tooth and a second tooth. The first tooth is arranged adjacent to the second tooth about a rotational axis of the motor. The assembly further comprises a first coil and a second coil. The assembly is configured to receive three winding phases comprising a first winding phase, a second winding phase, and a third winding phase. The first tooth and the second tooth form adjacent pairs of the stator teeth comprising two of the three winding phases, and the adjacent pairs of the stator teeth are distributed around the opening and form an opening configured to receive a rotor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 15/612,178 filed Jun. 2, 2017, entitled WINDING CONFIGURATION ELECTRIC MOTOR, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present device generally relates to an electric motor and more specifically relates to a stator assembly for a permanent magnet electric motor.

SUMMARY OF THE INVENTION

In at least one aspect, an electric motor stator comprises a yoke comprising an outer support. The yoke forms an opening configured to receive a rotor comprising a plurality of permanent magnets disposed in a plurality of rotor slots. A first tooth extends into the opening and comprises a first stem portion and a first arc portion. The first arc portion extends from the first stem portion forming a first receiving region configured to receive a first stator coil comprising a first number of turns in connection with a first electrical phase of a power supply. A second tooth extends into the opening adjacent the first tooth, and the first tooth and the second tooth form adjacent pairs of stator teeth extending into the opening. The second tooth comprises a second stem portion and a second arc portion. The second arc portion extends from the second stem portion forming a second receiving region configured to receive a second stator coil comprising a second number of turns in connection with a second electrical phase of the power supply. The stator is configured to receive three winding phases comprising the first winding phase, the second winding phase, and a third winding phase. Each of the adjacent pairs of the stator teeth comprises two of the three winding phases. Each of the first number of turns and the second number of turns are evenly distributed among the three winding phases connected to the adjacent pairs of stator teeth about the opening formed by the stator.

In at least another aspect, a stator assembly for a permanent magnet motor is disclosed. The assembly comprises a yoke forming an outer support configured to receive a rotor comprising a plurality of permanent magnets disposed in a plurality of rotor slots. A plurality of teeth are in connection with the yoke and extend into an opening formed by the yoke. The plurality of teeth comprise a first tooth and a second tooth. The first tooth is arranged adjacent to the second tooth about a rotational axis of the motor, and the teeth form a plurality of adjacent pairs of stator teeth. A first coil is in connection with a first electrical phase comprising a first conductive winding having a first number of turns in connection with the first tooth. A second coil is in connection with a second electrical phase comprising a second conductive winding having a second number of turns in connection with the second tooth. The first number of turns is different from the second number of turns. The stator assembly is configured to receive three winding phases comprising the first winding phase, the second winding phase, and a third winding phase. Each of the first number of turns of the first coil and the second number of turns of the second coil are evenly distributed among the three winding phases connected to the adjacent pairs of stator teeth about the opening.

In at least another aspect, a stator assembly for a permanent magnet motor is disclosed. The stator assembly comprises a yoke forming an outer support and a plurality of teeth in connection with the yoke. The plurality of teeth extend into an opening formed by the yoke and comprise a first tooth and a second tooth. The first tooth is arranged adjacent to the second tooth and the first tooth and second tooth form a plurality of adjacent pairs of stator teeth distributed about a rotational axis of the motor. A first coil comprises a first conductive winding having a first number of turns disposed around the first tooth. A second coil comprises a second conductive winding having a second number of turns disposed around the second tooth. The first number of turns is different from the second number of turns. The stator is configured to receive three winding phases comprising a first winding phase, a second winding phase, and a third winding phase. Each of the adjacent pairs of the stator teeth comprises two of the three winding phases forming the first coil and the second coil, and the adjacent pairs of the stator teeth are distributed around the opening and form an opening configured to receive a rotor.

These and other features, advantages, and objects of the present device will be further understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a projected view of an electric motor;

FIG. 2 is a cross-sectional view of a stator and a rotor of the electric motor demonstrated in FIG. 1 along section line II-II;

FIG. 3 is a cross-sectional view of a stator of the electric motor demonstrated in FIG. 1 along section line II-II; and

FIG. 4 is a partial cross-sectional view of a stator and the electric motor demonstrated in FIG. 1 along section line II-II in accordance with the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the device as oriented in FIG. 1. However, it is to be understood that the device may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

Referring to the embodiment illustrated in FIG. 1, a projected view of a motor 10 is shown. The motor 10 may correspond to a brushless permanent magnet (BPM) motor or a permanent magnet synchronous motor (PMSM). In various embodiments, the motor 10 may be configured to operate at high efficiency and interconnect via a motor shaft 12 to a pulley. Additionally, the motor shaft 12 may be coupled to a rotating assembly in a direct drive configuration. Accordingly, the motor 10 may be utilized in a variety of applications in accordance with the disclosure.

In an exemplary embodiment, the motor 10 may be configured to drive an operation of an appliance. For example, the motor 10 may be configured to power various devices including, but not limited to, compressors, fans, pumps, and washers. In some embodiments, the motor 10 may be configured to drive a rotational motion 14 of a washer drum of a washing machine. The motor 10 may be applied in a washer, dryer, or various appliances or machines and may be particularly beneficial in high-speed operations. The motor 10 may comprise an electrical connection 16, which may further be connected to a power supply, controller, or various forms of drive circuits. In this configuration, the motor 10 may be driven or operated by a controlled application of current signals to windings of a stator as illustrated and further discussed in reference to FIG. 2. As discussed further herein, the stator may comprise a beneficial winding configuration configured to improve efficiency during high-speed operation.

As illustrated in FIG. 1, the motor 10 may comprise a housing 18, which may comprise a plurality of mounting structures 20. The mounting structures 20 may be configured to engage a frame or structural supports to position and/or align the motor 10. In this configuration, the motor 10 may be positioned for alignment with a belt assembly or in connection with a coupler. Accordingly, the motor 10 may be utilized in a variety of applications without departing from the spirit of the disclosure.

Referring now to FIG. 2, a cross-sectional view along section line II-II demonstrated in FIG. 1 is shown. The cross-sectional view demonstrates an exemplary embodiment of a stator 22 and a rotor 24 of the motor 10 in accordance with the disclosure. The stator 22 may correspond to a concentrated winding stator forming a cylindrical opening 26 configured to receive the rotor 24 separated by an air gap 28. The rotor 24 may comprise a plurality of permanent magnets 30 disposed in a plurality of rotor slots 34 formed by a rotor core 32 of the rotor 24. In this configuration, the permanent magnets 30 and the rotor core 32 may form a magnetic structure attached to the motor shaft 12.

As shown, the permanent magnets 30 are inset within the rotor core 32. Though demonstrated as being disposed within the slots 34 of the rotor 24, the permanent magnets 30 may be attached to an exterior surface 36 of the rotor core 32. The permanent magnets 30 may be evenly distributed about a rotational axis 38 of the rotor 24 forming a pole pitch P. The pole pitch P in the exemplary embodiment is 45 degrees. However, the pole pitch P may vary depending on the number of permanent magnets 30 implemented in the rotor 24. For example, in an embodiment of the rotor 24 comprising six permanent magnets 30, the pole pitch may be 60 degrees.

During operation, the permanent magnets 30 generate a flux density distribution across the air gap 28. The main flux density of the rotor 24 is produced by the magnets 30. In various embodiments, the magnets 30 do not carry current from the operation of the motor 10. Accordingly, the losses incurred during operation of the motor 10 may be limited to losses in the rotor core 32 and the stator 22. For this reason, the motor 10 is suitable for applications where high efficiency is a concern. In addition to these benefits, the motor 10 may comprise a unique design and implement a plurality of stator coils 40 of the stator 22.

More specifically, the disclosure may provide for the stator 22 design to have a configuration that is particularly effective in achieving efficient, high-speed operation of the motor 10. The stator 22 may comprise a hybrid winding configuration of the stator coils 40. The hybrid winding configuration comprises an uneven distribution or alternating number of turns N of the windings 42 in adjacent or neighboring stator coils 40. The stator coils 40 may each be enclosed about a stem portion 43 forming a proximal end portion 44 of each tooth 46. Each tooth 46 may further comprise an arc portion 48 forming a distal end portion 50.

In an exemplary embodiment, the hybrid configuration of the coils 40 comprises an alternating configuration of a full coil 52 on a first tooth 46 a and a partial coil 54 on a second tooth 46 b. The full coil 52 may comprise a first number of turns N1, and the partial coil 54 may comprise a second number of turns N2. The first number of turns N1 of the full coil 52 may be greater than the second number of turns N2 of the partial coil 54. In this configuration, the stator 22 may provide for improved efficiency for high-speed operation through reduced current draw.

As demonstrated, each of the coils 54 may be connected to a winding phase A, B, and C of the motor 10. The winding phases may be evenly distributed angularly about a yoke 56 of the stator 22. For example, each of the winding phases A, B, and C (three phases in this example) may be connected in a repeating order to the teeth 46 extending from the yoke 56 of the stator 22. In this configuration, each of the windings 42 is connected to a corresponding phase of the winding phases A, B, and C, and the phases may be in conductive connection with the electrical connection 16 configured to supply driving current to the coils 54. In operation, the current may be applied to each of the winding phases A, B, and C in an offset phase timing, which may result in the rotational motion 14 of the rotor 24 and, consequently, a rotation of the motor shaft 12.

The hybrid configuration of the coils 40 as discussed herein may increase the efficiency of operation of the motor 10 by reducing current draw during operation. The reduced current draw may further lead to a reduction in temperature rise during operation that may result due to conductive losses, which increase at increased operating currents. Additionally, the hybrid configuration is particularly flexible and allows for high efficiency for differing bus voltage levels that may vary based on various applications and a geographic region of operation. Accordingly, the improved flexibility of the motor 10 may provide for reduced manufacturing cost resulting in limited variation that may otherwise result from manufacturing different motors for different applications and geographic locations.

Referring now to FIG. 3, an exemplary embodiment of the stator 22 is shown further demonstrating the alternating configuration of the stator coils 40. As discussed herein, hybrid winding configuration of the stator 22 may comprise an uneven distribution or alternating number of the windings 42. For example, each pair of adjacent teeth 60 or neighboring stator coils 40 may have a first tooth 46 a and a second tooth 46 b. The first tooth 46 a may comprise a first stem portion 43 a and a first arc portion 48 a. The second tooth 46 b may comprise a second stem portion 43 b and a second arc portion 48 b. In this configuration, the first tooth 46 a and the second tooth 46 b may comprise different dimensions and spacing configured to accommodate the full coil 52 and the partial coil 54, respectively.

As previously discussed, the full coil 52 may comprise a first number of turns N1 and the partial coil 54 may comprise a second number of turns N2. Accordingly, the first number of turns N1 of the full coil 52 may be greater than the second number of turns N2 of the partial coil 54. Additionally, the teeth 46 of the stator 22 may be configured to accommodate the full coil 52 and the partial coil 54. The terms partial and full, as used to describe the windings 42 of the stator coils 40, are intended to communicate a relative proportion of the coils 40 related to the number of turns N of the windings 42 of an exemplary embodiment of the motor 10 and shall not be considered limiting to various structures of the stator 22 and the motor 10.

In an exemplary embodiment, each of the teeth 46 is arranged in an alternating configuration of the first tooth 46 a and the second tooth 46 b. In order to accommodate the first number of turns N1, each of the first teeth 46 a may comprise the first stem width 62 a and the first arc length 64 a. In this configuration, a first winding slot 66 a may be formed by the first arc length 64 a extending beyond the first stem width 62 a, which may be configured to accommodate the first number of turns N1. Accordingly, the proportions of the first tooth 46 a may be configured to accommodate a larger number of the windings 42 than the second tooth 46 b.

In order to accommodate the second number of turns N2, each of the second teeth 46 b may comprise the second stem width 62 b and the second arc length 64 b. In this configuration, a second winding slot 66 b may be formed by the second arc length 64 b extending beyond the second stem width 62 b, which may be configured to accommodate the second number of turns N2. In this arrangement, the stem width 62 (e.g. the first stem width 62 a) and/or arc length 64 (e.g. the first arc length 64 a) of each of the plurality of the adjacent teeth 60 of the stator 22 may be configured in a variety of embodiments to accommodate the different proportions of the first number of turns N1 and the second number of turns N2. Such a hybrid winding scheme may be achieved while efficiently maintaining a relationship of the neighboring teeth 46 and a plurality of stator slots 68 formed therebetween.

The specific proportions and spacing of the teeth 46 of the stator 22 may further be based on a total number of teeth NT of the stator 22. In the exemplary embodiment, the stator 22 comprises 12 teeth (e.g., NT=12). In some embodiments, the number of teeth NT of the stator 22 may differ and may commonly correspond to a multiple of the number of winding phases (e.g., A, B, and C). For example, the number of teeth NT of the stator 22 may comprise 6, 9, 12, 15, etc. Based on the number of teeth NT and the proportions of each of the first teeth 46 a and the second teeth 46 b, the tooth pitch T may also be determined based on a desired spacing of the teeth 46 and separated by the stator slots 68.

Referring to FIG. 4, a detailed cross-sectional view of the stator 22 along section line II-II of FIG. 1 is shown. As illustrated in FIG. 4, the windings 42 and the pair of the adjacent teeth 60 are shown demonstrating further detail. The first number of turns N1 is shown wrapped around the first winding slot 66 a. The first winding slot 66 a may be formed by the first stem portion 43 a extending from the proximal end portion 44 in connection with the yoke 56 to the distal end portion 50 in connection with the first arc portion 48 a. In this configuration, a length L1 of the first tooth 46 a in combination with a first extension length 72 a or first arm length of the first arc portion 48 a may determine the dimensions of an opening formed by the first winding slot 66 a. The first winding slot 66 a may form a first receiving region 74 a configured to receive the first number of turns N1. The representation of the cross-section of the windings 42 demonstrated in FIGS. 2-4 may not correspond to a specific number of turns N of the windings 42 and may be exaggerated in proportions to demonstrate detail.

The second number of turns N2 is shown wrapped around the second winding slot 66 b. The second winding slot 66 b may be formed by the second stem portion 43 b extending from the proximal end portion 44 in connection with the yoke 56 to the distal end portion 50 in connection with the second arc portion 48 b. In this configuration, a length L2 of the second tooth 46 b in combination with a second extension length 72 b or second arm length of the second arc portion 48 b may determine the dimensions of an opening formed by the second winding slot 66 b. In this configuration, the second winding slot 66 b may form a second receiving region 74 b configured to receive the second number of turns N2.

Each of the receiving regions 74 a and 74 b may correspond to openings or areas formed by the winding slots 66 a and 66 b and configured to receive the windings 42 of the stator coils 40. Accordingly, the receiving regions may be proportioned based on the number of turns of the full coil 52 and the partial coil 54. The first number of turns N1 and the second number of turns N2 of the coils 40 may vary based on the specific design specifications of the motor 10. Additionally, the total number of turns of the windings 42 forming the full coil 52 and the partial coil 54 of the adjacent teeth 60 may be combined to determine a slot fill for a corresponding stator slot 68 between the adjacent teeth 60. Accordingly, the slot fill for each of the stator slots 68 may correspond to the total number of turns of the first number of turns N1 and the second number of turns N2.

For example, in an exemplary embodiment, the first number of turns N1 may be 176 and the second number of turns N2 may be 30. In this configuration, a turn ratio of the first number of turns N1 to the second number of turns N2 may be between 2:1 and 10:1. In some embodiments, the ratio of the first number of turns N1 to the second number of turns N2 may be between 4:1 and 8:1. In this particular example, the approximate ratio of the first number of turns N1 to the second number of turns N2 may be between 5:1 and 7:1 and, more specifically, may be approximately between 5.5:1 and 6.5:1. Accordingly, the ratio of the number of turns N of one or more neighboring pairs of the adjacent teeth 60 may be configured to suit the desired operation of the motor 10.

Similar to the ratio of the number of turns of the first tooth 46 a and the second tooth 46 b (N1:N2), the dimensions of the first winding slot 66 a and the second winding slot 66 b may be proportioned commensurate to the turn ratio to accommodate the number of turns N of the full coil 52 and the partial coil 54. For example, if the ratio of the first number of turns N1 of the first tooth 46 a to the second number of turns N2 of the second tooth 46 b is 6:1, the corresponding ratio of the first receiving region 74 a to the second receiving region 74 b may also be approximately 6:1. Accordingly, each of the neighboring pairs of the adjacent teeth 60 of the stator 22 may be appropriately sized to accommodate the first number of turns N1 and the second number of turns N2.

For purposes of this disclosure, the term “coupled” (in all of its forms, couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components. Such joining may be permanent in nature or may be removable or releasable in nature unless otherwise stated.

It is also important to note that the construction and arrangement of the elements of the device as shown in the exemplary embodiments is illustrative only. Although only a few embodiments of the present innovations have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, the length or width of the structures and/or members or connector or other elements of the system may be varied, the nature or number of adjustment positions provided between the elements may be varied. It should be noted that the elements and/or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be included within the scope of the present innovations. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the desired and other exemplary embodiments without departing from the spirit of the present innovations.

It will be understood that any described processes or steps within described processes may be combined with other disclosed processes or steps to form structures within the scope of the present device. The exemplary structures and processes disclosed herein are for illustrative purposes and are not to be construed as limiting.

It is also to be understood that variations and modifications can be made on the aforementioned structures and methods without departing from the concepts of the present device, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

The above description is considered that of the illustrated embodiments only. Modifications of the device will occur to those skilled in the art and to those who make or use the device. Therefore, it is understood that the embodiments shown in the drawings and described above is merely for illustrative purposes and not intended to limit the scope of the device, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents. 

The invention claimed is:
 1. An electric motor stator comprising: a yoke comprising an outer support and forming an opening configured to receive a rotor comprising a plurality of permanent magnets disposed in a plurality of rotor slots; a first tooth extending into the opening and comprising a first stem portion and a first arc portion, wherein the first arc portion extends from the first stem portion forming a first receiving region configured to receive a first stator coil comprising a first number of turns in connection with a first electrical phase of a power supply; a second tooth extending into the opening adjacent the first tooth, the first tooth and the second tooth forming adjacent pairs of stator teeth extending into the opening, the second tooth comprising a second stem portion and a second arc portion, wherein the second arc portion extends from the second stem portion forming a second receiving region configured to receive a second stator coil comprising a second number of turns in connection with a second electrical phase of the power supply; and wherein the stator is configured to receive three winding phases comprising the first winding phase, the second winding phase, and a third winding phase, wherein each of the adjacent pairs of the stator teeth comprises two of the three winding phases, and wherein each of the first number of turns and the second number of turns are evenly distributed among the three winding phases connected to the adjacent pairs of stator teeth about the opening formed by the stator.
 2. The stator according to claim 1, wherein the turn ratio between the first number of turns to the second number of turns is at least 2:1.
 3. The stator according to claim 1, wherein the first receiving region and the second receiving region are proportioned differently based on a turn ratio between the first number of turns and the second number of turns.
 4. The stator according to claim 1, wherein the first receiving region is defined as a first stem width of the first tooth extending along a first length of the first tooth and a first extension length of the first arc portion.
 5. The stator according to claim 4, wherein the first receiving region is configured to accommodate the first number of turns based on a plurality of first tooth parameters comprising the first stem width, the first length, and the first extension length.
 6. The stator according to claim 5, wherein the second receiving region is defined as a second stem width of the second tooth extending along a second length of the second tooth and a second extension length of the second arc portion.
 7. The stator according to claim 6, wherein the first receiving region is configured to accommodate the second number of turns based on a plurality of second tooth parameters comprising the second stem width, the second length, and the second extension length.
 8. The stator according to claim 7, wherein at least one of the first tooth parameters defining the first receiving region and second tooth parameters defining the second receiving region are proportioned differently based on a turn ratio between first number of turns and the second number of turns.
 9. The stator according to claim 1, wherein the plurality of the adjacent pairs of the stator teeth are distributed around the opening and form a cylindrical opening configured to receive a rotor.
 10. The stator according to claim 7, wherein the plurality of adjacent pairs of the stator teeth are evenly spaced around the opening and separated by a plurality of stator slots.
 11. A stator assembly for a permanent magnet motor, comprising: a yoke forming an outer support configured to receive a rotor comprising a plurality of permanent magnets disposed in a plurality of rotor slots; a plurality of teeth in connection with the yoke and extending into an opening formed by the yoke, the plurality of teeth comprising a first tooth comprising a first coil having a first number of turns and a second tooth comprising a second coil having a second number of turns, wherein the first tooth is arranged adjacent to the second tooth about a rotational axis of the motor, and the first tooth and the second tooth form a plurality of adjacent pairs of stator teeth; and wherein the stator assembly is configured to receive three winding phases comprising a first winding phase, a second winding phase, and a third winding phase, wherein each of the first number of turns of the first coil and the second number of turns of the second coil are evenly distributed among the three winding phases and two of the three winding phases are connected to each of the adjacent pairs of stator teeth.
 12. The stator assembly according to claim 11, wherein the first number of turns of the first coil comprises at least twice as many turns as the second number of turns of the second coil.
 13. The stator assembly according to claim 11, wherein the first tooth comprises a first stem portion extending into the opening from the yoke to a first distal end portion forming a first arc portion
 14. The stator assembly according to claim 13, wherein the first stem portion and the first arc portion form a first receiving region configured to receive the first number of turns of the first coil.
 15. The stator assembly according to claim 14, wherein the second tooth comprises a second stem portion extending into the opening from the yoke to a second distal end portion forming a second arc portion
 16. The stator assembly according to claim 15, wherein the second stem and the second arc form a second receiving region configured to accommodate the second number of turns of the second coil.
 17. The stator assembly according to claim 16, wherein the first receiving region is larger than the second receiving region.
 18. A stator assembly for a permanent magnet motor, comprising: a yoke forming an outer support; a plurality of teeth in connection with the yoke and extending into an opening formed by the yoke, the plurality of teeth comprising a first tooth and a second tooth, wherein the first tooth is arranged adjacent to the second tooth and the first tooth and second tooth form a plurality of adjacent pairs of stator distributed about a rotational axis of the motor; a first coil comprising a first conductive winding having a first number of turns disposed around the first tooth; a second coil comprising a second conductive winding having a second number of turns disposed around the second tooth, wherein the first number of turns is different from the second number of turns; and wherein the stator is configured to receive three winding phases comprising a first winding phase, a second winding phase, and a third winding phase, wherein each of the adjacent pairs of the stator teeth comprises two of the three winding phases forming the first coil and the second coil.
 19. The stator assembly according to claim 18, wherein the first number of turns and the second number of turns of the adjacent pairs of the stator teeth are evenly distributed among the winding phases connected to the adjacent pairs of stator teeth about the opening.
 20. The stator assembly according to claim 18, wherein the adjacent pairs of the stator teeth form a hybrid winding configuration comprising alternating coils comprising the first number turns and the second number of turns evenly distributed about the opening. 